未调用 NSMutableDictionary 的 Swizzled 方法 [英] Swizzled method for NSMutableDictionary is not getting called

问题描述

我正在尝试调整 NSMutableDictionary.我在这里做错了什么?我正在尝试为 NSMutableDictionary 覆盖 setObject:forKey:.

I'm trying to swizzle NSMutableDictionary. What am I doing wrong here? I'm trying to override setObject:forKey: for NSMutableDictionary.

#import "NSMutableDictionary+NilHandled.h"
#import <objc/runtime.h>


@implementation NSMutableDictionary (NilHandled)

+ (void)load{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        Class class = [self class];

        SEL originalSelector = @selector(setObject:forKey:);
        SEL swizzledSelector = @selector(swizzledSetObject:forKey:);

        Method originalMethod = class_getInstanceMethod(class, originalSelector);
        Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);

        class_replaceMethod(class, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod));

        BOOL didAddMethod = class_addMethod(class,originalSelector,method_getImplementation(swizzledMethod),method_getTypeEncoding(swizzledMethod));
        if (didAddMethod) {
            class_replaceMethod(class,swizzledSelector,method_getImplementation(originalMethod),method_getTypeEncoding(originalMethod));
        } else {
            method_exchangeImplementations(originalMethod, swizzledMethod);
        }
    });
}

- (void) swizzledSetObject:(id)anObject forKey:(id<NSCopying>)aKey
{
    [self swizzledSetObject:anObject?anObject:@"Nil" forKey:aKey];
}

@end

推荐答案

NSMutableDictionary 是一个 类簇.它是许多实现实际工作的 Apple 私有的具体子类的抽象基类.作为子类，它们覆盖 -setObject:forKey:.NSMutableDictionary 本身没有真正实现该方法，也没有尝试调用它.因此，没有什么会调用您的替换实现.

NSMutableDictionary is a class cluster. It is an abstract base class for a number of Apple-private concrete subclasses that implement the real work. As subclasses, they override -setObject:forKey:. There is no real implementation of that method on NSMutableDictionary itself and nothing attempts to call it. Therefore, nothing calls your replacement implementation.

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